微藻是一個很好水質汙染的處理者，廢污水中的氮和磷皆是微藻生長必要的元素，藉由微藻的處理可快速的淨化水質並且也相對的有高的生物質量產生，因此，相對而言微藻也是很好的燃料生產者，而且微藻擁有高的光合效率以及生長速率比其他能源作物快。但是通常利用微藻處理廢水的其中一個主要問題是在於微藻的回收，然而微藻固定化是其中一種解決之方式。 為了找出小球藻(Chlorella sp.)生長和營養鹽去除最佳操作參數，本研究先以不同C/N比濃度的光合異營培養為基礎，了解小球藻生長機制，接著利用這個最佳C/N比濃度，加入不同F/M的固定化顆粒與不同顆粒數，找出固定化培養的最佳生長條件。 實驗結果顯示，在不同C/N比濃度的光合異營培養下，C/N比為10時，擁有高的比生長速率為2.44 1/day，以及對氮與碳的去除量最高，分別為16.71 mg/g‧hr和86.99 mg/g‧hr。另外，在固定化培養實驗中，發現到顆粒越多，食微比越低，並不會使小球藻生長更好或是去除效果更好。除此之外，也發現到空白顆粒(沒包覆任何藻體)對營養鹽的去除效果良好，硝酸鹽氮和總有機碳分別共去除141 mg/L和684 mg/L，這表示空白顆粒可以吸附這些營養鹽，因此，在這個實驗中，當食微比為0.2和投入的顆粒數為6:1(v/v)時，對硝酸鹽氮和總有機碳量最高，分別去除141 mg/g‧hr和684 mg/g‧hr。Microalgae are useful material to treat wastewater. Nitrogen and phosphorus of the wastewater are the necessary elements of microalgae growth. Microalgae could quickly purify wastewater and also could generate a large amount of biomass. Microalgae are great producer for fuel because it has higher photosynthetic efficiency and growth rate than other energy crops. However, a big problem for using microalgae to treat the waste water is separation of the microalgae and liquid. Immobilization of microalgae is one of the solution methods for this problem. For finding out the optimum parameters of microalgae growth and nutrient removal, this study used the different C/N ratios of photosynthetic heterotrophic culture as basis to explore the mechanism of the microalgae growth. The different C/N ratios and F/M ratios of the immobilized particle number and particle size were tested to find out the optimum growth parameters of the immobilized culture. The results showed that the highest specific grower rate is 2.44 1/day in photosynthetic heterotrophic culture when the C/N ratio is 10. And the highest remove rate of N and C were 16.71 mg/g·hr and 86.99 mg/g·hr, respectively. Furthermore, in immobilized culture, the more of particle number and the less of the F/M ratio did not improve the Chlorella sp. growth and nutrient removal. In the blank experiment, the gel particle without seeding with microalgae, the nitrate nitrogen and total organic carbon were removed 141 mg/L and 684 mg/L, which indicated that the gel particle could absorb that nutrient. Therefore, in this study, when the F/M ratio is 0.2 and particle number is 6:1(v/v), the highest removed quantity of nitrate and total organic carbon were 141 mg/g·hr and 684 mg/g·hr, respectively.